The anatomy and relationships ofHaasiophis terrasanctus, a fossil snake by well-developed hind limbs from the Mid-Cretaceous of the Middle East

Abstract

The fossil snake speciesHaasiophis terrasanctusTchernov, Rieppel, Zaher, Polcyn, and Jacobs, 2000, from the early Upper Cretaceous of the Middle East, is described and illustrated, following a review of the current debate on snake relationships and origins. The description and discussion presented here adds important detail to the knowledge of this taxon and its phylogenetic significance beyond the limited account presented in the original description ofHaasiophis. The species is remarkable in that it shows the skull of a relatively advanced (i.e., macrostomatan) snake, yet preserves well-developed hind limbs. The hind limb includes a femur, tibia, fibula, astragalus, calcaneum, distal tarsal four, and remains of four metatarsals and two phalanges.Haasiophiscannot be considered a juvenile specimen ofPachyrhachis. The implications of the presence of well-developed hind limbs inHaasiophis, Pachyrhachis, andPodophisfor the cladistic analysis of the phylogenetic interrelationships of these fossil snakes is discussed. The presence of well-developed hind limbs inPachyrhachisandHaasiophisalso creates methodological problems for the cladistic analysis of the phylogenetic relationships of these fossil snakes. Scenarios of snake origins are reviewed and found to be deficient in the absence of a well-corroborated hypothesis of snake relationships within Squamata.